<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <link rel="stylesheet" href="css/bootstrap.css">
    <style>
        .row img{
            width:100%;
        }
        [class^="col"]{
            margin-top: 20px;
        }
    </style>
</head>
<body>
    <!-- 单一职责 -->
    <div class="container">
        <div class="row">
            <div class="col-md-4 col-sm-6">
                <img src="images/item01.jpg" alt="">
            </div>
            <div class="col-md-4 col-sm-6">
                <img src="images/item02.jpg" alt="">
            </div>
            <div class="col-md-4 col-sm-6">
                <img src="images/item03.jpg" alt="">
            </div>
            <div class="col-md-4 col-sm-6">
                <img src="images/item04.jpg" alt="">
            </div>
            <div class="col-md-4 col-sm-6">
                <img src="images/item05.jpg" alt="">
            </div>
            <div class="col-md-4 col-sm-6">
                <img src="images/item06.jpg" alt="">
            </div>
        </div>
    </div>
</body>
</html>